1*33de042dSApple OSS Distributions<h2>semaphore_create</h2> 2*33de042dSApple OSS Distributions<hr> 3*33de042dSApple OSS Distributions<p> 4*33de042dSApple OSS Distributions<strong>Function</strong> - Create a new semaphore. 5*33de042dSApple OSS Distributions<h3>SYNOPSIS</h3> 6*33de042dSApple OSS Distributions<pre> 7*33de042dSApple OSS Distributions<strong>kern_return_t semaphore_create</strong> 8*33de042dSApple OSS Distributions <strong>(task_t</strong> <var>task</var>, 9*33de042dSApple OSS Distributions <strong>semaphore_t</strong> <var>*semaphore</var>, 10*33de042dSApple OSS Distributions <strong>int</strong> <var>policy</var>, 11*33de042dSApple OSS Distributions <strong>int</strong> <var>value</var><strong>);</strong> 12*33de042dSApple OSS Distributions</pre> 13*33de042dSApple OSS Distributions<h3>PARAMETERS</h3> 14*33de042dSApple OSS Distributions<dl> 15*33de042dSApple OSS Distributions<dt> <var>task</var> 16*33de042dSApple OSS Distributions<dd> 17*33de042dSApple OSS Distributions[in task port] The task receiving the send right of the newly created semaphore. 18*33de042dSApple OSS Distributions<p> 19*33de042dSApple OSS Distributions<dt> <var>semaphore</var> 20*33de042dSApple OSS Distributions<dd> 21*33de042dSApple OSS Distributions[out send right] The port naming the created semaphore. 22*33de042dSApple OSS Distributions<p> 23*33de042dSApple OSS Distributions<dt> <var>policy</var> 24*33de042dSApple OSS Distributions<dd> 25*33de042dSApple OSS Distributions[in scalar] The blocked thread wakeup policy for the newly created semaphore. Valid policies are: 26*33de042dSApple OSS Distributions<dl> 27*33de042dSApple OSS Distributions<p> 28*33de042dSApple OSS Distributions <dt> SYNC_POLICY_FIFO 29*33de042dSApple OSS Distributions<dd> 30*33de042dSApple OSS Distributionsa first-in-first-out policy for scheduling thread wakeup. 31*33de042dSApple OSS Distributions <p> 32*33de042dSApple OSS Distributions <dt> SYNC_POLICY_FIXED_PRIORITY 33*33de042dSApple OSS Distributions<dd> 34*33de042dSApple OSS Distributionsa fixed priority policy for scheduling thread wakeup. 35*33de042dSApple OSS Distributions </dl> 36*33de042dSApple OSS Distributions <p> 37*33de042dSApple OSS Distributions<dt> <var>value</var> 38*33de042dSApple OSS Distributions<dd> 39*33de042dSApple OSS Distributions[in scalar] The initial value of the semaphore count. 40*33de042dSApple OSS Distributions</dl> 41*33de042dSApple OSS Distributions<h3>DESCRIPTION</h3> 42*33de042dSApple OSS Distributions<p> 43*33de042dSApple OSS DistributionsThe <strong>semaphore_create</strong> function creates a new semaphore, associates the 44*33de042dSApple OSS Distributionscreated semaphore with the specified task, and returns a send right 45*33de042dSApple OSS Distributionsnaming the new semaphore. In order to support a robust 46*33de042dSApple OSS Distributionsproducer/consumer communication service, Interrupt Service Routines 47*33de042dSApple OSS Distributions(ISR) must be able to signal semaphores. The semaphore synchronizer 48*33de042dSApple OSS Distributionsservice is designed to allow user-level device drivers to perform 49*33de042dSApple OSS Distributionssignal operations, eliminating the need for event counters. Device 50*33de042dSApple OSS Distributionsdrivers which utilize semaphores are responsible for creating (via 51*33de042dSApple OSS Distributions<strong>semaphore_create</strong>) and exporting (via <strong>device_get_status</strong>) 52*33de042dSApple OSS Distributionssemaphores for 53*33de042dSApple OSS Distributionsuser level access. Device driver semaphore creation is done at device 54*33de042dSApple OSS Distributionsinitialization time. Device drivers may support multiple semaphores. 55*33de042dSApple OSS Distributions<h3>RETURN VALUES</h3> 56*33de042dSApple OSS Distributions<dl> 57*33de042dSApple OSS Distributions <p> 58*33de042dSApple OSS Distributions<dt> <strong>KERN_INVALID_ARGUMENT</strong> 59*33de042dSApple OSS Distributions<dd> 60*33de042dSApple OSS DistributionsThe task argument or the policy argument was invalid, 61*33de042dSApple OSS Distributions or the initial value of the semaphore was invalid. 62*33de042dSApple OSS Distributions <p> 63*33de042dSApple OSS Distributions<dt> <strong>KERN_RESOURCE_SHORTAGE</strong> 64*33de042dSApple OSS Distributions<dd> 65*33de042dSApple OSS DistributionsThe kernel could not allocate the semaphore. 66*33de042dSApple OSS Distributions <p> 67*33de042dSApple OSS Distributions<dt> <strong>KERN_SUCCESS</strong> 68*33de042dSApple OSS Distributions<dd> 69*33de042dSApple OSS DistributionsThe semaphore was successfully created. 70*33de042dSApple OSS Distributions</dl> 71*33de042dSApple OSS Distributions<h3>RELATED INFORMATION</h3> 72*33de042dSApple OSS Distributions<p> 73*33de042dSApple OSS DistributionsFunctions: 74*33de042dSApple OSS Distributions<a href="semaphore_destroy.html"><strong>semaphore_destroy</strong></a>, 75*33de042dSApple OSS Distributions<a href="semaphore_signal.html"><strong>semaphore_signal</strong></a>, 76*33de042dSApple OSS Distributions<a href="semaphore_signal_all.html"><strong>semaphore_signal_all</strong></a>, 77*33de042dSApple OSS Distributions<a href="semaphore_wait.html"><strong>semaphore_wait</strong></a>, 78*33de042dSApple OSS Distributions<a href="device_get_status.html"><strong>device_get_status</strong></a>. 79